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´95 Eldo engine oscilation ?


FSchuett

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Hello,

if I uninstall and install these ISC must I observe anything ?

Can I adjustable these IPC if I was uncareful ?

What is the exact procedure to uninstall, clean und install these part ?

Frank

Frank,

To answer your quesions, the ISC can be removed, cleaned and reinstalled without affecting any calibrations. If you install a new one, you will have to set the length of the screw in stud that makes contact with the throttle linkage.

Study the pictures we have provided you in the previous posts for an idea of how the ISC and its mounting bracket are asembled.

As I mentioned, my hands are big and I could not remove the three nuts that hold the ISC to it's bracket while the bracket was installed. I had to free the bracket from the throttle body first. This is done by removing the throttle body

Remove the air cleaner ductwork to the throttle body. AT this point you may want to disconnect the 4-wire connector at the ISC and check continuity of the ISC contacts in question. The throttle lever, when closed, should be making contact with the plunger with sufficient force to CLOSE the contacts in the ISC. A small set of jumpers will permit you to clip your test lamp/meter to terminals A and B. (A and B are farthest from the hook that latches the connector.) Cycle the switch several times to proove it good or bad. I am betting on bad!

Remove the hot water hose to the throttle body. If you first remove the coolant pressure cap there will be no need to drain any coolant.

Unclip the throttle cable and remove the 4 bolts that hold the throttle body to the intake manifold.

The suplly and return hard fuel lines are clipped to the side of the ISC mounting bracket. NOTE carefully how they are attached so you can return them.

Rotate the throttle body out of the way and tilt the ISC bracket so the best position which will allow you to remove the ISC from the bracket.

With the ISC free you can remove the 3 mounting studs that hold the ISC together. Carefully separate the two sections and note that a couple gears can possibly fall free but only if you are a "klutz" ( is that German, my Mother used to call me that back in Minnesota?!)

you will see the set of contacts in the corner of the opened ISC and it is a simple matter to remove the oil residue from the contacts. Look for any sign of physical damage.

I believe that the gear lube off gasses enough fumes to cause these contacts to get dirty over time. Radio Shack sells a contact cleaner and enhancer called DeOxit and I am sure you can find the equivalent in Germany www.radioshack.com and look for item #64-4336. DeOxit is made by Caig.

Even sliding a piece of a matcbook cover through the points will work for a long time! Take a minute and remove any excess gear lube that is not doing anything as this will extend the intervals of cleaning. Here in Phoenix, the engine remains hot 24 hours a day if parked in the sun, thus accelerating problems that may never be seen in colder climates!

Reassemble the ISC and test the contact function on the work bench to confirm your work.

Return the ISC to it's bracket and reassemble. No special problems, just get everything back like you found it.

Let the forum know the results of your efforts.

Regards,

Jim in Phoenix

Jim in Phoenix

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Hello,

now, I´m cleaning the ISC last weekend and the problem is the same as before.

I´m clean the EGR-valve (with new gasket), the throttle body and ISC... nothing.

Any one an idea ?

With best wishes

Frank

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Hello,

now, I´m cleaning the ISC last weekend and the problem is the same as before.

I´m clean the EGR-valve (with new gasket), the throttle body and ISC... nothing.

Any one an idea ?

With best wishes

Frank

What were the results of your testing the ISC both before you cleaned it and after?

By pushing in on the plunger, you should have seen the contacts closing.

Jim in Phoenix

Jim in Phoenix

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  • 4 weeks later...

Hello,

i´m driving the last 3 week over 2000 mls and the problem is the same (without any error code).

Anyone an idea ?

Frank

Buy me an airline ticket! I'll pack up my tools and try my best to figure it out! laugh.gif

Frank, consider this. If you have a laptop. Consider buying http://www.autotap.com with exhanced GM parameters. Checking the parameters against normal ranges may point out a problem.

I don't know if a 95 has this but, I think it was Bruce that had a crack or split in a collar that connects the throttle body and intake manifold. The following is a photo. You have done a lot of work and have not found the problem, its time to look at odd ball items.

You cleaned the ISC motor contacts?

post-3-1130528122_thumb.jpg

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Hi fellows, After years of slight chuggle in my 93 Eldo TC the code

PO83 showed up as current for a day. About a year ago I changed the

Ignition control module and got rid of the PO83. But as it showed up again now

I changed both crankshaft sensors - required moving the front engine mount

a little to the side. Now the feeling of a more pronounced chuggle or miss is

gone -there is a very slight chuggle still though but I imagine that that is just

the PCM searching for the right mixture. The outside temp is now below

57 degrees so now the mixture is supposed to become a little richer anyway.

I bought a little resistor which is supposed to fool the computer when the temp is

above 57 - never put it in though. I never went through the cleaning of

the ISC either as I have never had any problem with idle.

So I suppose the new crank sensor A and B helped. Future will tell.

/Jan Linderholm

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  • 1 year later...

Hello,

now, 25.000 mls later my problem with the oscilation is the same...

I´ve clean all relevant parts (ISC motor contacts, EGR-valve, throttle body)

and install a new EGR gasket and fuel filter.

And... without any codes the problem is the same...

Anyone a idea ?

Frank

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Hello,

now, 25.000 mls later my problem with the oscilation is the same...

I´ve clean all relevant parts (ISC motor contacts, EGR-valve, throttle body)

and install a new EGR gasket and fuel filter.

And... without any codes the problem is the same...

Anyone a idea ?

Frank

I had the same experience with a Pathfinder I own in Mexico. I thought maybe it was Mexican gas - It is very noticeable because the road to my home there is downhill, with two stretches, probably a 20% grade, for a long block each. At about 1600 rpm, with my foot off the accelerator, and engine braking slowing the car down gradually for a few seconds, it feels as if I blipped the accelerator a tiny bit, and the rpms go to around 1900 or so, and then they go back down gradually to 1600 as a result of engine braking again, and so on.

So, I called a radio show mechanic - Leon Kaplan, in Los Angeles, who really seems to know cars, has a quality shop here. I described the symptom to him, and he knew precisely what I was talking about.

He said that it is normal - that fuel injected cars have this designed into the computer. It was awhile since I made the call, and I don't recall exactly why - the memory is fuzzy but it was something about fuel pressure buildup perhaps - but - this is a fuzzy memory. What was very clear, is: it isn't a problem.

So, I have ignored it, and the car runs fine.

Since your car has no codes, and the systems seem okay, I think you don't have a problem.

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Ok Caddyinfo members, lets try to help Frank. Here is a translation of Frank's symptoms translated from German to English:

Which I forgot to mention, while stationary and/or in the no-load operation am the number of revolutions constantly with approx.. 700 RPM without any Schankung. The speed fluctuations arise "only" when gas taking away, whereby it is largest in the range 1500 to 2500 RPM.

There then the number of revolutions varies over approx.. 200-300 RPM. As said, only when gas taking away within range mentioned above. Below approx.. 1400 and above approx.. 3000 RPM does not occur these fluctuations. For this reason, I believe it not at the ISC engine lie, since this regulates nevertheless only the idling speed, or not

****************************************************************************

PS there is no translation for Schankung my guess is SEARCHING. His uneven searching or fluctuations is above idle when he takes his foot off the gas moving while above idle up to 2500 RPM. I have to look at what that closed contact does in the ISC motor and get into the details. I have not had an ISC motor for a few years now, this is where we miss out guru.. quick answers

Did this engine have the mouse holes and phenolic plates? To me, that this happens upon deceleration it sounds like the ISC motor's closed throttle switch, what do you all think? What would cause this to happen in the 1500 to 2500 RPM RANGE?

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

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Although i cannot really help with the technical side of all this i can help a little with translating German into English.

Frank let me know if you need any translation help and i'm sure we can find the proper words together.

As a side note. i can't speak or write German but understand 60% to 70% when i hear or read it.

Also, i have the Service manual for the 1993 Eldo which includes the Northstar Engine and is almost the same car as the 95 i believe. again, let me know if i can be off help.

Marc.

If you are in complete control..... you are not going fast enough....

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Although i cannot really help with the technical side of all this i can help a little with translating German into English.

Frank let me know if you need any translation help and i'm sure we can find the proper words together.

As a side note. i can't speak or write German but understand 60% to 70% when i hear or read it.

Also, i have the Service manual for the 1993 Eldo which includes the Northstar Engine and is almost the same car as the 95 i believe. again, let me know if i can be off help.

Marc.

Thanks Marc, that's a great idea, Mike

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Hallo,

hier das Problem in deutsch...

Unter Last und in Leerlauf läuft der Motor einwandfrei.

Sobald ich jedoch während der Fahrt kein Gas oder nur sehr sehr wenig Gas gebe (Bergabfahrt etc.),

fängt die Drehzahl an zu schwanken z.B. von 1.600 runter auf 1.500 und wieder auf 1.600 UPM.

Diese Drehzahlschwankungen treten solange auf, bis das Fahrzeug steht, ich auf "N" schalte oder wieder beschleunige.

Ich habe folgende Maßnahmen schon erledigt:

EGR Ventil gereinigt, ISC Kontakte gereinigt, throttle body gereinigt, EGR Dichtung erneuert, Benzinfilter erneuert.

Die Abgaswerte und die Leerlaufdrehzahl ist einwandfrei.

Kann es sein, daß der Motor irgendwo Luft zieht ?

Zu wenig Benzin kann ich mir nicht denken, sonst würde die Leerlaufdrehzahl auch schwanken.

Verdrecktes, unsauberes oder minderwertiges Benzin kann ich mir hier in Deutschland auch nict vorstellen,

zumal ich 98 Oktan tanke.

Gruß

FSchuett

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ok, i guess i need to go bottom naked now..

Hello, here the problem in German language...

Under load and in idling, the motor runs flawlessly. However, as soon as I give no gas (going of hill) or only a little gas during the trip, the number of revolutions begins to surge for example from 1600 RPM down to 1500 and back again to 1600 RPM continiously.

This RPM surging keeps on happening until i put it in Neutral or accelerate again

I already done the following work: EGR valve cleaned, cleaned ISC contacts, cleaned throttle body, renewed EGR sealing, renewed gasoline filter.

The exhaust fume values are good and when idling the RPM's etc. are all perfect.

Could it be that the motor sucks some false air somewhere?

I do not think it's lean gasoline mix because then my idle rpm would surge as well.

I can not imagine filthy, unclean or inferior gasoline here in Germany especially since I use 98 octanes fuel (note from Marc : i cannot believe it's bad fuel as well. Especially in Germany provided Frank uses the 'normal' petrol stations like Shell for example)

Greetings blablabla Frank.

If you are in complete control..... you are not going fast enough....

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Yes, it could be that the engine "sucks some false air from some place", meaning that you might have a vacuum leak.. It might make sense for you to look at the rubber collar between the throttle body and the intake manifold and the intake manifold gaskets..

I hope others brainstorm on this also, this problem has gone on too long. How about the spacers/mouse holes does this engine have them?

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Mike, do you mean these rubber collars?

Edit: Cr*p... maximum of 64k allowed.. let me try to reduce the file size and still keep its quality reasonable

2nd Edit : ok, it's there but it's of bad quality. PM me to get the original if you want.

post-4273-1185553464_thumb.jpg

If you are in complete control..... you are not going fast enough....

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Mike, do you mean these rubber collars?

Cyr, there is a rubber collar between the rear of the throttle body and the intake manifold on the older years (95 and older, I think), they can develop cracks and suck air, that could definately cause a problem.

Logan recently had this problem as did someone else, I will try to find out who else it was recent Mike

Here is it, darn I am good, I have to ask Logan for a raise :lol: see the recent link here

http://caddyinfo.ipbhost.com/index.php?sho...46&hl=logan

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Mike, do you mean these rubber collars?

Cyr, there is a rubber collar between the rear of the throttle body and the intake manifold on the older years (95 and older, I think), they can develop cracks and suck air, that could definately cause a problem.

Logan recently had this problem as did someone else, I will try to find out who else it was recent Mike

Here is it, darn I am good, I have to ask Logan for a raise :lol: see the recent link here

http://caddyinfo.ipbhost.com/index.php?sho...46&hl=logan

I will put in a good word with Logan for your raise.. you never know it might help.

Anyway, see above picture, the upper vacuum collar was cracked in my case and i just simply put a tape around it, reconnected the vacuum hoses and all was fine again.

Mine was so cracked though (my own fault!) that i had an idle of 4-5000 rpm's.

That makes it all a little more easy to troubleshoot.

If you are in complete control..... you are not going fast enough....

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Hello Cyr,

today I´ve clean all parts (EGR, throttle body) and I inspected all rubbers...

nothing...

Now, I´ve found a distinction to you photo, look here:

post-1843-1185651604_thumb.jpg

It´s your photo, at my ´95 Eldo is the middle hose not available - YELLOW POINT -.

There is a plastic plug in the middle hole.

I think it´s original because all repairs are from GM and I´m the second owner.

If you want I make a photo...

In spite of that, the problem is the same :(

Frank

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Frank have you hooked up a vacuum gage to it?

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Frank have you hooked up a vacuum gage to it?

Hello,

no, I don´t have a vacuum gauge.

And I´ve checking all rubbers and lines, all are OK...

Now, what is a rubber collar and where is it ?

Frank

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Frank have you hooked up a vacuum gage to it?

Hello,

no, I don´t have a vacuum gauge.

And I´ve checking all rubbers and lines, all are OK...

Now, what is a rubber collar and where is it ?

Frank

Frank did you physically inspect the rubber seats?

The one at the back (without the yellow dot) can be easily pulled off and you can check if it has any cracks etc.

If you are in complete control..... you are not going fast enough....

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Frank have you hooked up a vacuum gage to it?

Hello,

no, I don´t have a vacuum gauge.

And I´ve checking all rubbers and lines, all are OK...

Now, what is a rubber collar and where is it ?

Frank

Frank did you physically inspect the rubber seats?

The one at the back (without the yellow dot) can be easily pulled off and you can check if it has any cracks etc.

Hello Cyr,

I´ve pulled off and check the two rubber at the back... it´s optical OK...

Here is a photo...

post-1843-1185708397_thumb.jpg

With two lines and a plug in the middle...

Frank

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